The specification describes a new and improved optical coupler which comprises (1) a substrate which is adapted to receive and reflect light, having formed therein and adjacent the major (or top) surface of the substrate an optical waveguiding structure comprising three interconnected light confining...http://www.google.de/patents/US4262995?utm_source=gb-gplus-sharePatent US4262995 - Planar star coupler device for fiber optics
